In recent years, optical connectors employing lenses that optically couple optical transmission lines together are attracting attention. A microlens is disposed at a predetermined distance from the tip of an optical transmission line such as an optical fiber. Light exiting from the optical transmission line is enlarged in accordance with the numerical aperture thereof and is then collimated by the microlens and coupled with the microlens of an opposing connector. In such a lens-type optical connector, light is enlarged and then collimated. Thus, compared to a butt joint type optical connector such that the tips of optical transmission lines are butted against each other, the tolerance for misalignment between connectors is large. In addition, since optical transmission lines are not contacted, it is good in durability.
However, the lens-type optical connector that enlarges light and then collimates it has the following problem. When an optical connector is disengaged, collimated submillimeter-sized parallel light may enter the eyes of a user or worker (laser hazard). In particular, an optical signal for high-speed communication has a wavelength of 850 nm or more, and is invisible to the naked eye. At present, in order to reduce this risk, the connector housing is provided with a shutter. While the connector is engaged, the shutter is housed in the housing. When the connector is disengaged, the shutter is automatically lowered to suppress light leakage.
Particularly in the case of multifiber connectors, the same type of tape shaped optical transmission lines are often connected to perform transmission and reception. For this reason, the connectors on both sides have to be provided with shutters, and the connectors increase in size. In addition, conventional shutters provided in connectors are easily opened and closed with a finger, and thus the risk of laser hazard is not sufficiently removed.
There is known a structure for suppressing laser hazard such that a relay ferrule is disposed between an adapter and an optical connector. When the optical connector is disconnected, the lens of the adapter and the entrance end face of the relay ferrule are spaced a sufficient distance away from each other to suppress optical coupling. When the optical connector is connected, the relay ferrule is moved forward to the focal point of the lens along the optical axis. (See, for example, Japanese Laid-open Patent Publication No. 5-323151.)